You can cite information in your PowerPoint presentations to show that you've done the research for your topic. Don't present information found from others as if it's your own work, even if it's in a PowerPoint presentation. You can cite works in PowerPoint through the use of footnotes on a slide, endnotes after your slides or the notes attached to your slides. Use the citation style of your academic or professional discipline, and remain consistent between the PowerPoint and any printed works that accompany it.
Create a footnote in PowerPoint to show the reference on that slide. Click on the "Insert" tab and then click "Text Box." Click and drag to draw the box on the slide. Typically a footnote will be in the lower left corner of the slide. Type the citation information according to the standards of your citation guidebook. If you have multiple footnotes on one slide, you can create a superscript number before each one. Type the number, and then click and drag with the mouse to highlight it. Press "Ctrl+Shift+Plus" on the keyboard.
Use an endnote system to have all of the citations collected at the end of the presentation on their own slide. Type a number after the material to be cited, and then click and drag to highlight it. Press "Ctrl+Shift+Plus" to make it superscript and then repeat that number on the notes slide to indicate which material corresponds to which work cited.
Include the citations in the notes section of PowerPoint if you're going to give your audience a handout of your slides after the presentation. In the main slide design screen, click in the "Notes" section below the slide. Type in your citation. It will be saved with PowerPoint. When you print the slides, choose the "Notes Page" layout to include the citations. This keeps the text off the slide and allows your presentation to move more smoothly.